Understanding Smoke and Carbon Monoxide Detectors | Ask This Old House

[@Dredpath1]

This is very important. As a fire alarm and life safety technician, many people don’t know the difference and it’s something that people should know. A lot of people thinks it’s an annoying thing on the wall/ceiling, but it’s job is to save lives.

[@lailas.3205]

"I keep getting indicators that I'm at the end of my life." Omg cracked me up!!! 🤣🤣

[@jefflebowski918]

A note on 2020 NEC code: all new work requires hardwired smoke detectors to be on a AFCI circuit breaker. GFCI protection is not required though.

[@KrazyKajun602]

Jeff, Is it required you have to do hardwired detectors for new residential? Can you not do wireless interconnected with a alarm system?

[@billz4795]

good review. Note that in many areas only sealed batteries are now code , and 10 year old units must be replaced. Also if you could include this in a future presentation and the intergration of a "system sensor" and how they are intergrated and uses.

[@shanew7361]

Great video and VERY important. 🙏

[@Sparky-ww5re]

Understanding the difference between the two technologies used in smoke alarms can mean the difference between life and death. Ionization alarms responds better to fast flaming fire producing little smoke, such as a cooking oil fire quickly spreading to towels, cabinets and so on. Photoelectric alarms respond better to slow smoldering fire producing heavy smoke such as caused by a lit cigarette dropped on a sofa, which also happens to be one of the most dangerous type of home fires due to the toxic fumes released. Dual sensor smoke alarms that combine both technologies in one unit offers maximum safety and should installed even if the authority having jurisdiction doesn't require them.

[@itran888]

Do you have a link of combo smoke and carbon monoxide alarm? I want to buy one but your video doesn’t show more details.

[@Icutmetal]

Is your Google broken?

[@dontaskmeforusername]

Google spies and there's no good search engine alternatives

[@duaneulman9915]

Thank you good information vary helpful.

[@ms.ladietoyou8672]

It helped me out . Thanks buddy

[@jackfarrell4727]

Great information thank you for the video. I have a question, what is the best place for a CO detector, on ceiling, wall and if wall how high?

[@kataysmith9581]

This is off subject but Kevin reminds me so much of the old time actor Van Johnson. He looks like him and his verbal comments are spot on. I wonder if he has ever been told that?

[@dmitry92203]

I've always heard that you should mount CO2 alarms near the floor. NOT on the ceiling like a smoke alarm.

[@awhitecouple]

A heating/ plumbing company told me the same thing. I bought one off of them for 250.00 they said the ones you get at the store may not go off in time.

[@AlexiHolford]

@@awhitecouplewhat a weird user name

[@n3wy3ar83]

@@AlexiHolford😂😂

[@jackfarrell4727]

That's what I'm talking about

[@ColoRadio6996]

First Alert makes a great product..

[@spritemarie]

I have a question. If your smoke detectors are hard wired and test correctly work, do you still have to replace them? Mine were installed around 1983.

[@nick3720]

Replace them with newer models as soon as possible.

[@Off-Grid]

Our CO alarm keeps going off lately. I think it's from heat in the attic coming down out of a vent. I'm also a little concerned the spray foam in the attic has something to do with it since there is a smell when it gets around 80 up there.

[@Matt-mq1ep]

You need to get that serviced and checked ASAP! Burn chamber in furnace could be leaking. Had a neighbor almost died from same issue.

[@Off-Grid]

@@Matt-mq1ep we have Mini-Splits so no exhaust to cause CO. By heat I meant typical attic space temperature.

[@Matt-mq1ep]

@@Off-Grid i see, weird that it would set a CO alarm off tho?

[@Off-Grid]

@@Matt-mq1ep yeah, I have no idea at the moment.

[@4WDriver]

@@Off-Grid call your local Fire Department and have them come out and test for CO. This will verify whether your detector is malfunctioning or not. Heat alone couldn't set off a CO detector. It's either malfunctioning, or something (possibly the spray foam you mentioned off-gassing if it is not an approved type installed by reputable installer; large amounts of mold or bacteria hidden away in the walls/rafter spaces; or an outside source such as a neighbor's furnace having an exhaust facing an area of your home where air comes in through; etc.) is introducing CO to your home and you need to figure it out and solve it. Don't brush off a CO alert, it's there to save your life.

[@patriciasamsel6004]

If I have 8 hardwired fire alarms in the house that communicate with each other, can I have one or more different types and will they still communicate with each other? For example, If I have one of the following combo of hardwired alarms will they still communicate: 1) 6 photoelectric + 2 combo photoelectric + CO alarms, 2) 6 photoelectric fire alarms + 2 ionic alarms, 3) 6 photoelectric alarms + 2 combo photoelectric-ionic alarms in which a few may or may not also be CO alarms?

[@clivemorgan7632]

Thank for the video

[@dontaskmeforusername]

I've noticed these are UL listed. is it okay if they aren't?

[@grantmeyer03]

Always wondered if smoke rises and Carbon monoxide sinks, how does does the system detect both?

[@RatKindler]

Carbon monoxide doesn't sink. See this from the First Alert company web site on where to place the detector: "Carbon Monoxide Alarms can be placed at any height on a wall or ceiling. It is a common misunderstanding that Carbon Monoxide Alarms must be placed near the ground to accurately detect levels of CO. In truth, Carbon Monoxide is roughly the same weight as air, and distributes evenly throughout a room. This means a CO detector can be placed at any height on a wall or ceiling."

[@bjs2022]

@@RatKindler Thank you for that. I have edited my initial comment. Some articles on the Internet state 2 feet below the ceiling and 2 feet above the floor so that the unit is where there is better air circulation.

[@4WDriver]

It's not CO that sinks, that would be LP, or propane gas. An explosive gas detector (yet another piece of important life-saving equipment, which detects gas leaks) must be placed near the floor for propane detection, and up by the ceiling for natural gas detection due to propane being heavier than air, and natural gas (methane) being lighter than air.

[@jefflebowski918]

CO is slightly lighter than air, it's CO2 that's heavier than air.

[@Sparky-ww5re]

​@@4WDrivergood to know. Just curious, are you aware of any states or cities that require explosive gas detectors in addition to smoke and CO alarms? Because I currently work as a residential electrician doing mostly new construction in South Carolina in Greenville County and surrounding counties, and none of them required us to install explosive gas detector outlets as of 2023, and all but a small handful of homes I'm involved with have natural gas (or propane in areas where natural gas is unavailable).

[@joellacecil7474]

Is the green light suppose to be on on the carbon monoxide detector ?

[@MUAADHMOHAMMEDMOHSENAL-QUSARI]

Thanks , I have a question which is , what is the suitable detector in firefighting that can be used in the car parking in the basement, remember that we have smoke that comes out of automobile exhaust?

[@Fredengle]

Photo electric should be fine in a parking garage but it could be suseptible to freezing in which case the heat alarm is the one you need in freezing temps but heat will only activate if it gets hot it cant detect smoke

[@newhorizonsintuitiveguidance]

Thanks for the update on the new technology in smoke detectors/fire alarms. Very educational. If you haven't already, please do a video on the standard battery operated ones most people still have in their homes.

[@MandoFettOG]

That was this video

[@farazmansoor3386]

Brilliant

[@The1025RChannel]

Technically smoke alarms not smoke detectors, at least by code definition. Smoke detectors do not make any sound and are connected to a fire alarm panel. Yes they both detect smoke, but the difference is important.

[@davidconaway239]

You can buy interconnected battery detectors

[@mattparr3038]

Does the carbon monoxide detectors work with home fireplaces? I've got a wood burner, obviously the wood I get is untreated.

[@AAAA-lt9hq]

If different jurisdictions can't agree on proper fire safety, how is the consumer to make an informed decision?

[@matthewstone5576]

Is there any such thing as an ionization plus photoelectric combo unit?

[@mrlibowski493]

Yes there is, look closely at the box when he shows the ten year battery units. Kidde also makes a combo unit. Like he says, I don't know what kind of fire going to have. A good reason to put CO at outlet height, is when it emenates from a lower level such as a basement, it trips before it reaches head height in bed.

[@Fredengle]

please see this article by nih about co : pubmed.ncbi.nlm.nih.gov/21536403/ and realize texas A & M has stated that ionization where its supposedly better is 20% failure in flaming fires and over 50 % failure in smoldering my former bussiness consulatant who is now a member of UL 217 actually contributed to some of the First U.S legislation to mandate Photo electric only it has an approximate failure of 4 for both smoldering and flaming fires this is from TExas A & M University

[@brucerauch8024]

My smoke detectors have a PI model number for both photo and ionization detection.

[@sterlingodeaghaidh5086]

Quick note: Ionization smoke detectors have a small amount of radioactive material in it, that's what makes the detector work, the best thing to do is send those detectors to a specialist disposal facility in your town, such as a hazardous materials depot as even tho its a small amount it can still cause issues if the containment vessel is breached.

[@Off-Grid]

Problem is no place will take them and they have no idea about any hazardous material. Same with lithium batteries. Home Depot used to take them but they stopped several years ago.

[@sterlingodeaghaidh5086]

@@Off-Grid I actually have about 5 places that take hazardous waste including stuff like that. Then again I am also in a region where giant chemical trailers are in random fields so I’m not exactly in the average are of the U.S. I will say normally the same people who regulate where you put them will also tell you where best to dispose of them when the time comes.

[@donc-m4900]

Our town 'dump' takes detectors.also all typs of batteties. Not sure why everyone doesn't take lithium, we need lithium for all the new electric cars. should be a good market for them.

[@Off-Grid]

@@donc-m4900 we didn't buy lithium batteries for our Off-Grid home because they weren't easily recyclable. Instead we did AGM Lead Acid, which is fully recyclable and we can actually get money back for them. Hopefully they'll make a better battery that's recyclable and holds more power before we have to replace our current ones.

[@sterlingodeaghaidh5086]

@@Off-Grid They have, and its on the market, but its new so it may take a bit for it to be widely accepted.

[@GC83163]

They left out low voltage detectors, which you probably have if you're home has a wired security system. Bonus with low voltage is only one battery to change that is located in the panel. Other then that pretty much the same.

[@threeleggedman]

New Jersey house built in 1970, now on the market. Are smoke alarms required in each bedroom to pass fire inspection? My realtor says no. She says one on each floor. I'm not so sure of that. What say you?

[@LJ-ft1ic]

I realize that this reply is a little late, but anyway, NFPA 72 (the National Fire Alarm and Signaling Code) requires that smoke alarms be present in each bedroom. That is a National Code, but is not mandatory unless your municipality incorporates NFPA 72 into their Building Code (directly or by reference).

[@garyg8036]

Watch on KZbin : What type of smoke alarm is best for your home - CBS Minnesota

[@djfremen]

Confused how the red interconnect wire triggers the other alarms. I just replaced all 6 with Co2 & smoke and wasn't' able to test. What happens when backup battery engaged?

[@Off-Grid]

You run a 14/3 wire between each alarm. The extra red wire goes to the red on the alarms. Then when alarm goes off it sends a signal down the red wire to the next alarm which sets it off and so on. If you have an older house that does not have this extra wire and you are unable to run one then you'd need to go with the wire less option.

[@MikeHoughtonasUnit8720]

my state has overkill as to how many.

[@CNM3]

yeah 10 years my butt these things get dirty and set off constant nuisance alarms even if you clean them most of the time you're going to end up having to permanently disable them. I had 3 of them go bad after just 4 years.

[@AmeraMuhammad-f9k]

I push the test button on my hard wired smoke detector and it never said warning carbon monoxide. Called the fire department and he said that didn't mean anything he talked for about five minutes then sent someone out. Theÿ were coughing and said. His expensive machine didn't pick up anything. He only stayed in one spot with his expensive machine. I tested the smoke detectors before and they never said warning carbon monoxide. What can I do.

[@bettymaverick1098]

Per experts in the field you should always purchase a Combo photoelectric and ionization. The others are a bad idea. After learning from real experts I removed my old detectors and installed the new Combo type. Always purchase a separate CO2 detector. You can read the many reasons why. Please check with real experts. Many places require hard wired ones but again there are problems with them also. Please read about from true experts. They do catch fire at times. Please do more research do not rely on this article alone.

[@sethjohnson4845]

Please link to real, true experts.

[@OGCJ10]

What experts ? Link your source of information

[@djijspeakerguy4628]

Co2 is carbon dioxide, the stuff you breath out. Carbon Monoxide abbreviation is CO. Probably 75% of people make this mistake, so don’t feel too bad.

[@bjs2022]

He failed to explain where carbon monoxide detectors should should not be mounted and how high on the wall. Some articles on the Internet state at least 2 feet below the ceiling and 2 feet above the floor. Also, not in areas of high humidity and temperature (direct sunlight?).

[@donc-m4900]

I do believe your statement is incorrect.

[@bjs2022]

@@donc-m4900 Thank you, I was misinformed. A representative of my utility or the fire department told me that during a home inspection. I have changed my initial comment: He failed to explain where carbon monoxide detectors should should not be mounted and how high on the wall. Some articles on the Internet state at least 2 feet below the ceiling and 2 feet above the floor. Also, not in areas of high humidity and temperature (direct sunlight?).

[@monkeyoperator1360]

@@bjs2022 if you're using combo units you want them not near the end of a hall/corner and about a foot off the ceiling. anywhere that has "dead" or standing air you dont wanna put a smoke alarm

[@Fredengle]

the actual answer is you should see this thing from the NIH : pubmed.ncbi.nlm.nih.gov/21536403/

[@isaacmorse6082]

CAUTION!! Smoke detectors go on the ceiling, Carbon Monoxide detectors go near the floor! Carbon monoxide is heavier and will start lower so the detectors should be below the level of your head when sleeping. Separate devices, separate locations, hard wired is preferable but combo detectors are the dumbest thing. Just my opinion.

[@clownhands]

I think you have shower steam triggering ionization not photoelectric reversed.

[@Kirby7601]

Sad that I can't even have hardwired alarms here without sacrificing to take down the walls just to add electrical circuits for these alarms

[@Matt-mq1ep]

A good electrician should be able to fish wiring through house without much trouble.

[@Kirby7601]

@@Matt-mq1ep not if conduit is required by law

[@rupe53]

@@Kirby7601 ... conduit is not required in most residential situations. (not by national codes)

[@Kirby7601]

@@rupe53 chicago is one of them

[@rupe53]

@@Kirby7601 ... there are places with local code. Sometimes that sucks. BTW, code is not LAW. Code is a set of rules that are not enforceable by the police.

[@gagalove18]

anyone know of a smart detector which also has the third wire to talk to others (or no such product exist as of yet)? thinking of replacing couple with smart ones and keeping rest of the old ones (not smart ones).

[@danielortiz6907]

Nest is your best bet

[@gpjadams2]

I wish the one that says they last 10 years would last 10 years. I just got 4 years and 8 months out of one of those.

[@chrisc5726]

10 years?? Riiiiight. Just like the eco bulbs life hours.

[@bg147]

I don't understand. If the photoelectric detector is triggered by smoke, I would expect it to be triggered by steam.

[@Noah-qt3rq]

Steam still lets some light pass through. Smoke will block the light.

[@djijspeakerguy4628]

Dust and insects, on the other hand… If you have a photoelectric sensor, ALWAYS have a stock of canned air dusters, don’t just take them down or remove the battery if they keep going off, as this is against code. Unfortunately, over half of all houses I’ve been in either have missing smoke alarms or ones with the battery removed. These people likely opted for the cheap ionization sensors that set off with shower or cooking steam.

[@cyndee3855]

My Carbon Monoxide detector has a constant green light and a flashing red light every 50 secs or so. Is the constant green light normal?

[@AutoUnder]

If it’s hardwired yes that’s normal, the green light just shows it’s receiving mains power

[@MrJoeweightman]

Funny but not funny the garage trips it because there are dangerous amounts ppm detected, as its supposed to do but we ignore this?

[@s_boyd378]

I know too much about smoke and co alarms. If u want to know more, hit me up.

[@Tesnobay]

If I have Kidde Smoke Alarms and CO detectors in my home today that are approaching 10 yrs, can I buy new Kidde alarms and interchange them without rewiring or taking down the mounts?

[@s_boyd378]

@@Tesnobay what model do you have and what model are planning to get?

[@Tesnobay]

@@s_boyd378 I don't have that info, it was a generic question

[@s_boyd378]

@@Tesnobay I would say most likely yes.

[@jimholmes2555]

With Carbon Monoxide being heavier than air, using a ceiling mount CO monitor, when your room fills up with CO the alarm will sound off telling you that you are dead.

[@pangushk]

That's a myth. CO2 is heavier but CO is actually slightly lighter than air (about 80% N2, 20% O2)

[@jimholmes2555]

@@pangushk look it up in the Pocket Ref. By Thomas Glover.

[@pangushk]

@@jimholmes2555ppl make mistakes. Know your chemistry , google it, ask some experts

[@pangushk]

Why don’t you google it?

[@jimholmes2555]

@@pangushk for one thing, Google is misspelled. American mathematician, Edward Kasner ask his nephew to come up with a name for a big number, a one followed by one hundred zeros. The boy called it a Googol. How accurate is Google going to be when they can't even spell their name right.

[@miker.1804]

Why do they go off at 2am? Is it to mess me up for the rest of the night? Never anytime other time..think it’s a conspiracy..

[@claro371]

Two problems with this video. If you are sleeping you cannot smell smoke. Second these are smoke alarms not smoke detectors.

[@jonathankleinow2073]

"I keep getting indications that I'm at the end of my life..." Kevin? You okay, buddy?

[@flat-earther]

I don't think he is, what a crazy thing to say...

[@russstrough3849]

Why don't you comment on how the regulations benefit the smoke detector manufacturers? They built the ones that failed then used their influence to write the regulations that require a 700 sq. ft. 2 bedroom cottage to have 5 smoke detectors and two CO2/smoke detectors hardwired and interconnected. Where's the proof that this over kill saves lives vs. lines the pockets of the corrupt manufacturers. Same deal with circuit breakers now costing $50 a piece.

[@2loco]

I live under a tree, so I don't need any of this nonsense.

[@bjs2022]

Alarms don’t “go off”, they are always on (unless they loose power) and they sound. And, they are not “hard wired” if there is a removable plug connector on both ends of the wires. Accuracy in technology presentations, please.

[@donc-m4900]

I get what you are saying. Example, my Dr. told me to lower my sodium intake. I never eat Na (bad things happen immediately). Now eating Salt (NaCL) on the other hand, it is in all my processed foods.

[@MattAlexanderMe]

In English, "go off" refers to an alarm ringing, in that context. You might be thinking of "turn off". And when you buy that "hardwired" alarm, guess what's in the box? The receiving end of that harness. Which requires what? That's right. Hardwiring.

[@bjs2022]

@@MattAlexanderMe Thank you for the clarification. He showed one end with a plug connector for the unit so the other end must have been the stripped wire. About alarms “going off“, I was corrected by the company that installed an alarm on my truck. They said the proper terminology is “arm”, “disarm“, and “sounds“.

[@rupe53]

@@bjs2022 ... yes, it's not "technology" but proper terminology when describing things.

[@newhorizonsintuitiveguidance]

I don't think you are clear on what "hard-wired" means. Hard-wired: to make (a function) a permanent feature in a computer by means of permanently connected circuits, so that it cannot be altered by software. This includes removable plug connectors which have been designed for those who appreciate this convenience when and if they need it. I certainly appreciate it. I love having options like this with any technological stuff.

[@lewiskelly14]

Another half baked video

[@Off-Grid]

Seemed informative to me, especially to those who don't know anything about them.

[@newhorizonsintuitiveguidance]

How so? Please elaborate. I found it to be informative on the new technology of smoke detectors/fire alarm systems. Most households still have the old standard battery ones.

[@dominicbonavita2.087]

First comment

[@johnlebzelter4208]

Your cool #not

[@todd2456]

@@johnlebzelter4208 "you're"

[@OfficalMasonSoda]

Second coment

[@johnlebzelter4208]

Who cares ?

[@todd2456]

@@johnlebzelter4208 You do. You responded.

[@johnlebzelter4208]

@@todd2456 no. Just tired of seeing it